I've applied for taxes since 2016 and always get GST/HST but this year I applied first time by TurboTax. Should I apply for this credit manually or is it already applied?

You only need to file your return and the GST credit will be claimed for you if you are eligible. To see if you will get an amount please follow the steps in your return as seen in the image below, starting by scrolling down in the menu on the left.

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